1. Field of the Invention
The present invention relates to machine components or parts with a tensile strength of greater than 2000 MPa for alternating mechanical stresses up to a temperature of about 160° C., formed from a thermally quenched and tempered steel alloy. In particular, the invention relates to the engine components and/or drive train components of vehicles.
2. Discussion of Background Information
In modern technology machine components subjected to alternating mechanical load stress are increasingly more highly loaded, up to the limits of the respective material resistance. This applies in particular to components of vehicles, because the weight reductions achieved thereby are also useful for savings in terms of fuel and the like.
High values for the toughness, strength and ductility property profile in the thermally quenched and tempered state are demanded of the materials from which the components are made, because these properties are of crucial importance for a dimensional design of the parts.
As became evident, due to the failure of parts in sustained operation material fatigue also needs to be taken into account in order to achieve a high operational reliability.
For parts subjected to major mechanical alternating stress in the field of railways, automobiles and aircraft, alloyed, optionally low-alloy quenched and tempered steels are generally used at present. A preferred representative of these steels is the alloy according to DIN material no. 1.6928. This rather low-alloy material contains 1.40 to 1.90% by weight of silicon in order to largely ensure high endurance strength. An attempt has also been made to increase the silicon content of this alloy up to 3.0% by weight in order to achieve the best fatigue properties of the material when the parts are under stress.
The use of steel alloys with a composition according to that of quenched and tempered steels of the aforementioned type has proven to be useful for a production of highly stressed machine components according to the prior art, but the fatigue properties thereof are often not sufficient for a mechanical alternating stress of a material which is used in the limit value range.
It would be advantageous to be able to provide machine components or parts with a tensile strength of greater than about 2,000 MPa which are to be subjected to alternating mechanical stresses in the thermally quenched and tempered state up to a temperature of about 160° C. and have much improved long-term properties and a high modulus of elasticity.